Petrogenesis of Ophiolites

A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (31 December 2016) | Viewed by 28009

Special Issue Editors

Geosciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam
Interests: genesis of chromitites and associated platinum group minerals; soil and environmental geochemistry; petrogenetic processes in ophiolites; abiotic methane in ultramafic rocks; quality assessment of aggregates and industrial minerals
Special Issues, Collections and Topics in MDPI journals
Andalusian Institute of Earth Sciences (IACT), Spanish National Research Council (CSIC), Armilla, 18100 Granada, Spain
Interests: igneous petrology; experimental petrology; high-temperature geochemistry; crustal anatexis; melt inclusions

Special Issue Information

Dear Colleagues,

Unravelling Earth’s history always attracts the interest of geoscientists and ophiolites represent a great proxy for understanding the development of large provinces of our planet. Ophiolites comprise key suites to understanding Earth’s Mantle and Oceanic Crust development and geotectonic evolution. Study of ore deposits in these complexes, like chromite, platinum-group minerals, copper, etc., may also significantly contribute in the determination of certain petrogenetic processes in the Earth’s interior. Apart from this, such concentrations in ophiolites comprise some of the largest ore deposits of high economic importance. This Special Issue aims to gather a number of widely accessible, peer-reviewed publications that will present recent developments on the petrogenesis of ophiolites, including magmatic and metamorphic assemblages, as well as their metallic concentrations. Contributions from geoscientists who deal with mineralogy, petrology, geochemistry, structural features, and mapping of ophiolites are very welcome.

Dr. Basilios Tsikouras
Dr. Antonio Acosta-Vigil
Guest Editors

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Keywords

  • mafic and ultramafic rocks
  • chromites
  • platinum group minerals
  • geotectonic evolution
  • mantle development
  • oceanic crust
  • plagiogranite
  • rodingite
  • cumulate rocks
  • ore deposits
  • metasomatic phenomena

Published Papers (4 papers)

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Research

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4593 KiB  
Article
New Occurrence of Pyroxenites in the Veria-Naousa Ophiolite (North Greece): Implications on Their Origin and Petrogenetic Evolution
by Aikaterini Rogkala, Petros Petrounias, Basilios Tsikouras and Konstantin Hatzipanagiotou
Geosciences 2017, 7(4), 92; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences7040092 - 21 Sep 2017
Cited by 26 | Viewed by 5652
Abstract
The Veria-Naousa ophiolite represents a dismembered unit in north Greece, which includes variably serpentinised lherzolite and harzburgite, locally intruded by a sparse network of dykes or thin layers of websterite and olivine-orthopyroxenite composition. The websterite and the olivine-orthopyroxenite show abundant petrographic and geochemical [...] Read more.
The Veria-Naousa ophiolite represents a dismembered unit in north Greece, which includes variably serpentinised lherzolite and harzburgite, locally intruded by a sparse network of dykes or thin layers of websterite and olivine-orthopyroxenite composition. The websterite and the olivine-orthopyroxenite show abundant petrographic and geochemical evidence (relic olivines with mantle affinities, Cr-rich spinels, low Al2O3, depletions in incompatible elements, and concave upwards rare earth element patterns) that they comprise replacive bodies from refractory subarc mantle precursors. The occurrence of these pyroxenites in dykes implies that channelled percolation of melts account for their replacive character. High CaO/Al2O3, low Zr and crystallisation of diopside suggest that a melt of ankaramitic/carbonatitic composition percolated in lherzolite replacing porphyroclastic olivine and forming the pyroxenes in the websterite. At a shallower level, harburgites were impregnated by boninitic melts (inferred by U-shape rare earth element patterns and very rich in Cr spinels) triggering the replacement of porphyroclastic olivine by orthopyroxene for the formation of olivine-orthopyroxenite. These peritectic replacements of olivine commonly occur in a mantle wedge regime. The peculiar characteristics of the Veria-Naousa pyroxenites with LREE and compatible elements enrichments resemble the subarc pyroxenites of Cabo Ortegal implying a similar environment of formation. Whole-rock and mineralogical (spinel and clinopyroxene) compositions are also in favour of a backarc to arc environment. It is recommended that the evolution of the Veria-Naousa pyroxenites record the evolution of the subarc region and the opening of a backarc basin in a broad SSZ setting in the Axios Zone of eastern Greece. Full article
(This article belongs to the Special Issue Petrogenesis of Ophiolites)
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7071 KiB  
Article
Ophiolitic Remnants from the Upper and Intermediate Structural Unit of the Attic-Cycladic Crystalline Belt (Aegean, Greece): Fingerprinting Geochemical Affinities of Magmatic Precursors
by Christina Stouraiti, Iakovos Pantziris, Charalampos Vasilatos, Christos Kanellopoulos, Panagiotis Mitropoulos, Panagiotis Pomonis, Robert Moritz and Massimo Chiaradia
Geosciences 2017, 7(1), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences7010014 - 21 Mar 2017
Cited by 25 | Viewed by 8394
Abstract
The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for understanding the Mesozoic tectonic evolution of the Aegean region. Unresolved questions concern their tectono-stratigraphic relationships across the region. The mode of occurrence of the Cycladic ophiolites varies, as they [...] Read more.
The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for understanding the Mesozoic tectonic evolution of the Aegean region. Unresolved questions concern their tectono-stratigraphic relationships across the region. The mode of occurrence of the Cycladic ophiolites varies, as they appear as: (a) dismembered blocks (olistoliths) within the supra-detachment units of Paros and Naxos; (b) mélange formations in the upper structural unit of western Samos and Skyros; and (c) meta-ophiolitic mélange in the Cycladic Blueschist Unit (CBU) from central Samos. The trace element geochemistry and Pb-Sr-Nd isotopes of the mafic ophiolitic rocks indicate four geochemical groups: (a) the upper unit metabasites from Paros and western Samos (Kallithea) display an evolved basaltic composition (Mg# 40.2–59.6), with low Zr/Nb values (5–16) and high Ce/Y values (1.3 to 2.6) compared to MORB, indicating island-arc tholeiite affinities; (b) Naxos upper unit metabasalts show spider diagrams patterns indicating ocean island basalt (OIB-type) affinities; (c) Central Samos metagabbros (CBU) are primitive rocks with Back-Arc Basin basalt affinities; (d) the Skyros metadolerites and Tinos (Mt Tsiknias) and S. Evia (CBU) metagabbros, cluster as a separate geochemical group; they exhibit high MgO values (>10 wt %), very low TiO2 values (0.1–0.2 wt %), Y and Yb, and depleted trace element N-MORB normalized patterns, similar to volcanic rocks formed in modern oceanic fore-arc settings, such as boninites. A combination of the Pb- and Sr-isotopic compositions of Cycladic metabasites indicate that the Pb and Sr incorporated in the Cycladic ophiolites correspond to mixtures of magmatic fluids with seawater (206Pb/204Pb = 18.51–18.80; 207Pb/204Pb = 15.59–15.7; 208Pb/204Pb = 39.03–39.80 and initial 87Sr/86Sr80 = 0.705–0.707). Furthermore, peridotite relicts from Samos, Paros, and Naxos—irrespective of the structural unit—display chemical affinities of ocean floor peridotites formed in a supra-subduction zone. The characteristics of harzburgite relicts in Cycladic serpentinites and Skyros indicate a highly residual nature of the mantle source. Geochemical data from this study shed further light on the complex structure of the oceanic lithosphere from which the Cycladic ophiolites originated. Full article
(This article belongs to the Special Issue Petrogenesis of Ophiolites)
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3190 KiB  
Article
Petrogenetic Implications for Ophiolite Ultramafic Bodies from Lokris and Beotia (Central Greece) Based on Chemistry of Their Cr-spinels
by Panagiotis Pomonis and Andreas Magganas
Geosciences 2017, 7(1), 10; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences7010010 - 03 Mar 2017
Cited by 7 | Viewed by 5677
Abstract
Cr-spinels from ultramafic rocks from Lokris (Megaplatanos and Tragana), and Beotia (Ypato and Alyki) ophiolitic occurrences were studied. These rocks comprise principally harzburgite with minor dunite. Small amounts of clinopyroxene-rich harzburgite and lherzolite have been observed along with the harzburgite in Alyki. The [...] Read more.
Cr-spinels from ultramafic rocks from Lokris (Megaplatanos and Tragana), and Beotia (Ypato and Alyki) ophiolitic occurrences were studied. These rocks comprise principally harzburgite with minor dunite. Small amounts of clinopyroxene-rich harzburgite and lherzolite have been observed along with the harzburgite in Alyki. The Cr# in the studied spinels displays a wide variability. The spinels hosted in harzburgite and cpx-rich harzburgite display low Cr# (<0.6), typical for oceanic (including back-arc basins) ophiolites, whereas the spinels hosted in dunite with Cr# (>0.6) characterize arc-related ophiolitic sequences. Cr-spinels from Alyki indicate a moderate fertile character and are analogous to those from abyssal peridotites. The dunitic and harzburgitic spinel–olivine pairs are consistent with a Supra-Subduction Zone origin. The relatively large range in spinel Cr# and Mg# may have been resulted from a wide range of degrees of mantle melting during the evolution of the host peridotites. Full article
(This article belongs to the Special Issue Petrogenesis of Ophiolites)
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Review

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9260 KiB  
Review
The Betic Ophiolites and the Mesozoic Evolution of the Western Tethys
by Encarnación Puga, Antonio Díaz de Federico, Mark Fanning, José Miguel Nieto, José Ángel Rodríguez Martínez-Conde, Miguel Ángel Díaz Puga, José Antonio Lozano, Gianluca Bianchini, Claudio Natali and Luigi Beccaluva
Geosciences 2017, 7(2), 31; https://0-doi-org.brum.beds.ac.uk/10.3390/geosciences7020031 - 20 Apr 2017
Cited by 32 | Viewed by 7108
Abstract
The Betic Ophiolites consist of numerous tectonic slices, metric to kilometric in size, of eclogitized mafic and ultramafic rocks associated to oceanic metasediments, deriving from the Betic oceanic domain. The outcrop of these ophiolites is aligned along 250 km in the Mulhacén Complex [...] Read more.
The Betic Ophiolites consist of numerous tectonic slices, metric to kilometric in size, of eclogitized mafic and ultramafic rocks associated to oceanic metasediments, deriving from the Betic oceanic domain. The outcrop of these ophiolites is aligned along 250 km in the Mulhacén Complex of the Nevado-Filábride Domain, located at the center-eastern zone of the Betic Cordillera (SE Spain). According to petrological/geochemical inferences and SHRIMP (Sensitive High Resolution Ion Micro-Probe) dating of igneous zircons, the Betic oceanic lithosphere originated along an ultra-slow mid-ocean ridge, after rifting, thinning and breakup of the preexisting continental crust. The Betic oceanic sector, located at the westernmost end of the Tethys Ocean, developed from the Lower to Middle Jurassic (185–170 Ma), just at the beginning of the Pangaea break-up between the Iberia-European and the Africa-Adrian plates. Subsequently, the oceanic spreading migrated northeastward to form the Ligurian and Alpine Tethys oceans, from 165 to 140 Ma. Breakup and oceanization isolated continental remnants, known as the Mesomediterranean Terrane, which were deformed and affected by the Upper Cretaceous-Paleocene Eo-Alpine high-pressure metamorphic event, due to the intra-oceanic subduction of the Jurassic oceanic lithosphere and the related continental margins. This process was followed by the partial exhumation of the subducted oceanic rocks onto their continental margins, forming the Betic and Alpine Ophiolites. Subsequently, along the Upper Oligocene and Miocene, the deformed and metamorphosed Mesomediterranean Terrane was dismembered into different continental blocks collectively known as AlKaPeCa microplate (Alboran, Kabylian, Peloritan and Calabrian). In particular, the Alboran block was displaced toward the SW to occupy its current setting between the Iberian and African plates, due to the Neogene opening of the Algero-Provençal Basin. During this translation, the different domains of the Alboran microplate, forming the Internal Zones of the Betic and Rifean Cordilleras, collided with the External Zones representing the Iberian and African margins and, together with them, underwent the later alpine deformation and metamorphism, characterized by local differences of P-T (Pressure-Temperature) conditions. These Neogene metamorphic processes, known as Meso-Alpine and Neo-Alpine events, developed in the Nevado-Filábride Domain under Ab-Ep amphibolite and greenschists facies conditions, respectively, causing retrogradation and intensive deformation of the Eo-Alpine eclogites. Full article
(This article belongs to the Special Issue Petrogenesis of Ophiolites)
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